The present invention relates to an electrode structure that is formed by using a semiconductor processing technique and a manufacturing method of a thin-film structural body.
FIG. 17 is a cross-sectional view showing a conventional electrode structure, which shows a thin-film structural body 101 installed in the electrode structure. The thin-film structural body 101 includes a supporting portion 103 and a floating portion 105 supported by the supporting portion 103, and is formed above a substrate 107 by using a conductive material. The floating portion 105, which is placed with a predetermined distance from the substrate 107, extends outwards from an upper portion of the supporting portion 103.
The substrate 107 includes a substrate main body 111, a first insulating film 113, a wiring 115 and a second insulating film 117. The first insulating film 113 is formed on the substrate main body 111. The wiring 115 is provided on the surface of the first insulating film 113, and the surface of the first insulating film 113 and the surface of the wiring 115 are substantially flattened without a step portion. The second insulating film 117 covers the surfaces of the wiring 115 and the first insulating film 113 and side faces thereof. Here, the second insulating film 117 has a hole section 117a which opens on the surface of the wiring 115 so that the surface of the wiring 115 is selectively exposed. The supporting portion 103 is formed on the wiring 115 through the hole section 117a. 
FIGS. 14 to 16 are cross-sectional views showing a sequence of conventional manufacturing processes of a thin-film structural body. First, as shown in FIG. 14, a sacrifice film 121 is formed on the entire surface of the substrate 107. In this stage, the second insulating film 117 has no hole section 117a in the substrate 107.
Next, a dry etching process is carried out from the surface side of the sacrifice film 121 so that an opening 121a is formed in the sacrifice film 121 while a hole section 117a is formed in the second insulating film 117; thus, an anchor hole 122 is formed so that the surface of the wiring 115 is selectively exposed. Consequently, a structure shown in FIG. 15 is obtained.
Next, as shown in FIG. 16, a thin-film layer 123 is formed on the sacrifice film 121 and the substrate 107 exposed through the anchor hole 122 by using a conductive material.
Thereafter, the thin-film layer 123 is selectively removed, with the result that residual portions of the thin-film layer 123 thus patterned are allowed to form a thin-film structural body 101. Successively, the sacrifice film 121 is removed so that a structure shown in FIG. 17 is obtained. Among the residual portions of the thin-film layer 123, the portion fitted into the anchor hole 122 forms the supporting portion 103 and the portion located on the sacrifice film 121 forms the floating portion 105.
In such a conventional manufacturing method, the sacrifice film 121 is desirably formed by using a material which is easily removed by etching, and, for example, a silicon oxide film is employed. With respect to the substrate main body 111, a silicon substrate is employed so that a semiconductor processing technique capable of fine manufacturing processes can be applied thereto. Further, in order to easily form the first insulating film 113 on the silicon substrate, a silicon oxide film is also employed to the first insulating film 113 in the same manner as the sacrifice film 121.
In order to prevent the first insulating film 113 from being also etched upon etching the sacrifice film 121, a material which is less susceptible to etching for the silicon oxide film and is easily processed, such as a silicon nitride film, is employed as the second insulating film 117.
However, in the case where the second insulating film 117 allows the surface of the wiring 115 to be completely exposed, etchant used for etching the sacrifice film 121 tends to invade between the side face of the wiring 115 and the second insulating film 117 and reach the first insulating film 113.
FIG. 18 is a plan view showing the structure of FIG. 15 when viewed from the opening side of the anchor hole 122. In the case where the anchor hole 122 on a plan view has a rectangular shape, a square or the like, with acute corners 122a stresses tend to concentrate on these corners. For this reason, there is a high possibility that a crack generates from each of these corners into the sacrifice film 121, the first insulating film 113 and the second insulating film 117. In particular, in the case where a silicon nitride film is used to form the second insulating film 117, its residual stress is exerted in the stretching direction while the residual stresses in the sacrifice film 121 and the first insulating film 113, made of a silicon oxide film, are exerted in the compressing direction; therefore, it is considered that this structure is more susceptible to cracks. The generation of such cracks not only causes a problem with strength, but also results in a higher possibility of etchant for use in etching the sacrifice film 121 reaching the first insulating film 113.
An object of the present invention is to provide an electrode structure and a manufacturing method of a thin-film structural body, which can remove a sacrifice film without removing other insulating films. Moreover, another object of the present invention is to provide an electrode structure and a manufacturing method of a thin-film structural body, which can suppressing the generation of cracks.
In a first aspect of an electrode structure, the electrode structure includes: a wiring (45) selectively placed on a first insulating film (33); a second insulating film (47) covering the first insulating film, selectively covering the wiring, and having a hole section (47c), said hole section entering the wiring inward by a first predetermined distance (d1) from an edge (45a) of a surface of the wiring to selectively expose the surface of the wiring; a sacrifice film (51) having an opening (51a) selectively exposing the surface of the wiring, and selectively formed on at least the second insulating film; and a thin-film layer (53) made of conductive material connected to the surface of the wiring selectively exposed through the opening and the hole section.
According to the first aspect of the electrode structure, since the hole section covers the first predetermined distance from the edge of the surface of the wiring, the invading path into the first insulating film of etchant to be used for etching the sacrifice film is lengthened. This reduces the possibility of that the etchant reaches the first insulating film. Thus, even when the first insulating film and the sacrifice film are made of the same material, it is possible to reduce the possibility of the first insulating film being etched in the etching process of the sacrifice film.
A second aspect of the electrode structure according to the present invention is the first aspect of the electrode structure, and the hole section (47c) is filled with the thin-film layer (53).
According to the second aspect of the electrode structure, it is possible to effectively prevent the invasion of the etchant to be used for etching the sacrifice film.
A third aspect of the electrode structure according to the present invention is the second aspect of the electrode structure, and the opening (51a) is opened so as to retreat from the hole section (47c) by a second predetermined distance (d2).
According to the third aspect of the electrode structure, it is possible to make a portion supporting a floating structure of the thin-film layer thicker, and consequently to increase the strength of the structure.
A fourth aspect of the electrode structure according to the present invention is the third aspect of the electrode structure, and the opening (51a) is filled with the thin-film layer (53).
According to the fourth aspect of the electrode structure, it is possible to lengthen the invading path to the first insulating film of the etchant to be used for etching the sacrifice film.
A fifth aspect of the electrode structure according to the present invention is the first aspect of the electrode structure, and the hole section (47c) has a polygonal shape with rounded corners (47r) or an elliptic shape on a plan view.
According to the fifth aspect of the electrode structure, since there are no corners in a plane shape of the hole section, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
A sixth aspect of the electrode structure according to the present invention is the first aspect of the electrode structure, and the opening (51a) has a polygonal shape with rounded corners (51r) or an elliptic shape on a plan view.
According to the sixth aspect of the electrode structure, since there are no corners in a plane shape of the opening, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
A seventh aspect of the electrode structure according to the present invention includes: a wiring (45) selectively placed on a first insulating film (33); a second insulating film (47) covering the first insulating film, selectively covering the wiring, and having a hole section (47c), said hole section entering the wiring inward by a first predetermined distance (d1) from an edge (45a) of a surface of the wiring to selectively expose the surface of the wiring, a residual stress of which is different from a residual stress of the first insulating film in direction; and a conductive thin-film structural body having a supporting portion (23b) connected to the surface of the wiring selectively exposed through the hole section, and a floating portion (23a) supported by the supporting portion with a predetermined distance from the second insulating film.
According to the seventh aspect, since the hole section (47c) of the second insulating film, a residual stress of which is different from a residual stress of the first insulating film, is placed with the first predetermined distance from the edge 45a of the surface of the wiring, it is possible to reduce a shearing stress exerted between the two elements.
An eighth aspect of the electrode structure according to the present invention is the seventh aspect of the electrode structure, and the supporting portion (23b) covers the hole section (47c).
According to the eighth aspect of the electrode structure, since the supporting portion is connected to both of the second insulating film and the wiring formed on the first insulating film, it is possible to reduce the possibility of the first insulating film and the second insulating film separating from each other.
In the eighth structure of the electrode structure, for example, the residual stress of the first insulating film (33) is a compressive stress while the residual stress of the second insulating film is a tensile stress. Moreover, for example, the first insulating film (33) is an oxide film and the second insulating film is a nitride film.
A ninth aspect of the electrode structure according to the present invention is the seventh aspect of the electrode structure, and the hole section (47c) has a polygonal shape with rounded corners (47r) or an elliptic shape on a plan view.
According to the ninth aspect of the electrode structure, since there are no corners in a plane shape of the hole section, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
A tenth aspect of the electrode structure according to the present invention is the seventh aspect of the electrode structure, and the opening (51a) has a polygonal shape with rounded corners (51r) or an elliptic shape on a plan view.
According to the tenth aspect of the electrode structure, since there are no corners in a plane shape of the opening, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
According to the electrode structure of the present invention, the surface of the first insulating film and the surface of the wiring are preferably placed on the same plane.
A first aspect of a manufacturing method of a thin-film structural body according to the present invention includes the steps of: (a) selectively forming a wiring (45) on a first insulating film (33); (b) forming a second insulating film (47) on the wiring and the first insulating film; (c) selectively removing the second insulating film to form a hole section (47c) which enters the wiring inward from an edge (45a) of a surface of the wiring by a first predetermined distance (d1) so that the surface of the wiring (45) is selectively exposed; (d) forming a sacrifice film (51) on the second insulating film; (e) selectively removing the sacrifice film to form an opening (51a) exposing the surface of the wiring so that an anchor hole (52) is formed; (f) forming a thin-film layer (53) on the anchor hole and the sacrifice film with a conductive material; and (g) removing the sacrifice film by etching.
According to the first aspect of the manufacturing method of a thin-film structural body, since the hole section covers the first predetermined distance from the edge of the surface of the wiring, it is possible to lengthen the invading path into the first insulating film of etchant to be used for etching the sacrifice film. Thus, even when the first insulating film and the sacrifice film are made of the same material, it is possible to reduce the possibility of the first insulating film being etched in the etching process of the sacrifice film at step (g).
A second aspect of the manufacturing method of a thin-film structural body according to the present invention is the first aspect of the manufacturing method of a thin-film structural body, and the opening (51a) is opened so as to retreat from the hole section (47c) by a second predetermined distance (d2).
According to the second aspect of the manufacturing method of a thin-film structural body, it is possible to make a portion supporting a floating structure of the thin-film layer thicker, and consequently to increase the strength of the structure. Moreover, with an arrangement in which the anchor hole is filled with the thin-film layer at step (f), it is possible to lengthen the invading path to the first insulating film of etchant to be used for etching the sacrifice film.
A third aspect of the manufacturing method of a thin-film structural body according to the present invention is the first aspect of the manufacturing method of a thin-film structural body, and the hole section (47c) has a polygonal shape with rounded corners (47r) or an elliptic shape on a plan view.
According to the third aspect of the manufacturing method of a thin-film structural body, since there are no corners in a plane shape of the hole section, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
A fourth aspect of the manufacturing method of a thin-film structural body according to the present invention is the first aspect of the manufacturing method of a thin-film structural body, and the opening (51a) has a polygonal shape with rounded corners (51r) or an elliptic shape on a plan view.
According to the fourth aspect of the manufacturing method of a thin-film structural body, since there are no corners in a plane shape of the opening, it is possible to avoid concentration of residual stresses, and consequently to suppress the generation of cracks.
In the manufacturing method of a thin-film structural body of the present invention, for example, the first insulating film (33) and the sacrifice film (51) are oxide films, and the second insulating film (47) is a nitride film.
In the manufacturing method of a thin-film structural body according to the present invention, a surface of the first insulating film and the surface of the wiring are preferably placed on a same plane.
These and other objects, features, aspects and advantages of the present invention will become more apparent in conjunction with the following detailed description and the accompanying drawings.